Detergents with a content of suds-stabilizing silicones are known, for example, from DE-OS 20 50 768, corresponding to U.S. Pat. No. 3,829,386, and DE-OS 23 38 468, corresponding to U.S. Pat. No. 3,933,672. These silicones are organopolysiloxanes, such as alkylpolysiloxanes and arylpolysiloxanes, particularly dimethylpolysiloxane, also their copolymers and block-polymers with polyalkylene oxides, especially ethylene oxide, as well as their acylation products with long-chained carboxylic acids. Usually the silicones used as suds-stabilizers contain 0.2% to 10% by weight of highly dispersed silica or highly dispersed aluminum oxide, where the highly dispersed silica is obtained, for example, by thermal dissociation of silicon tetrachloride or by precipitation from silicate solutions and which can be made hydrophobic by the action of silicon-organic compounds.
Normally quantities of 0.1% by weight of a silicone already suffice to make detergents of ordinary composition suds stable for use in drum-type household washing machines. However, considerable technical difficulties are presented to disperse such small quantities homogeneously in a wash powder. If the silicone is dispersed in the aqueous mixture (slurry) provided for hot spray-drying, a substantial part of the suds-stabilizing action is already lost in the subsequent spray drying, so that it is necessary to use a double to four-fold amount of the rather expensive silicone to get the desired result. It has, therefore, been repeatedly suggested to mix the silicones with solid carriers, such as the builder salts or the per compounds, or to embed them in a carrier material and to mix the granular premix obtained with the bulk of the detergent, preferably as a spray-dried hollow sphere powder. This requires, however, a weight-controlled mixing process, which increases the costs. A disadvantage is also that the additional mixing process may lead to a partial destruction of the hollow sphere structures and to increased dust formation.
It has also been suggested to atomize the suds-stabilizing silicone through a separate spray nozzle leading into the spray tower and to obtain this way a uniform distribution of the suds-stabilizer. But it was found that the known organopolysiloxanes can only be atomized to sufficiently small droplets under great difficulties, due to their special surface-active properties. Rather large drops are mostly formed, which lead to a substantially nonhomogeneous distribution and inadequate suds-stability of the detergent. In addition, the silicones come in direct contact with the detergent components, particularly the surfactants, so that the effect of the suds-stabilizers is again partly lost during the subsequent storage of the detergents.